The present invention relates to data storage devices, storage device control methods and magnetic disk drives and, more particularly, to data storage devices, storage device control methods and magnetic disk drives in which the setting of read operation parameters is controlled.
Devices using various types of media such as optical disks and magnetic tapes are known as information recording and reproducing devices. Among them, hard disk drives have become popular as storage devices for computers to such an extent that they are one of the storage devices indispensable for today's computers. Further, not limited to computers, their application is widening more and more due to the superior characteristics with the advent of moving picture recording/reproducing devices, car navigation systems, removable memories for digital cameras and so on.
Each magnetic disk used in hard disk drives has a plurality of tracks formed concentrically and each track is partitioned into a plurality of sectors. In each sector, sector address information and user data are stored. Either data write to a sector or data read from the sector is enabled by the head which accesses the desired sector according to the sector address information. A signal read out from a magnetic disk through data read operation is subjected to waveform shaping, decoding processing and other prescribed signal processing by a signal processing circuit before being transmitted to the host. Typically, a signal from a head is subjected to waveform equalization processing by an analog filter, converted to a digital signal by an AD converter and again subjected to waveform equalization processing by a waveform equalizer. Further, the signal from the waveform equalizer is subjected to decoding processing and demodulating processing.
It is possible that data cannot be read out accurately from a magnetic disk in the read operation. This is attributable to optimum read operation parameters which vary depending on the operating condition, particularly the temperature to which the hard disk drive is exposed. It is known that the amplitude and width of an analog waveform signal retrieved from the magnetic disk depend on magnetic characteristics (coercivity, residual magnetization, etc.) of the magnetic disk and the head-to-disk distance. The head-to-disk distance, magnetic disk's coercivity, MR head's resistance sensitivity and so on change with temperature. Accordingly, the characteristics of the reproduced waveform signal also change with temperature.
As such, techniques for detecting the temperature and changing parameters according to the detected temperature are known (for example, see Japanese Patent Laid-Open No. 9-102102). In that Japanese reference, a disk controller receives temperature data generated through a temperature sensor and an A/D converter. Further, pre-record compensation amount data, record current magnitude data, analog pre-filter cutoff frequency data, analog pre-filter equalization coefficient data and waveform equalizer coefficient data, which depend on the temperature, are respectively sent from the disk controller to the pre-record compensation amount setting register, record current magnitude setting register, analog pre-filter cutoff frequency setting register, analog pre-filter equalization coefficient setting register and waveform equalization coefficient setting register. With this, the pre-record compensation circuit, record current generation circuit, analog pre-filter and waveform equalizer can be set optimally according to the changing temperature. Thus the magnetic disk device can operate under optimum condition regardless of temperature fluctuations.